This invention is directed to a novel flow control valve, and more particularly, is directed to a novel flow divider-combiner valve.
A flow divider-combiner valve is generally designed for use with a system which uses a pressurized hydraulic fluid to drive at least two hydraulic cylinders, motors, or the like, one such being driven independently of the other. Such a valve functions as a flow divider when a single stream of hydraulic fluid, from a hydraulic fluid source, flows through the valve and thereby is divided into at least two hydraulic fluid streams. When flow of hydraulic fluid through such a valve is reversed, the valve functions as a flow combiner to combine several such hydraulic fluid streams.
For example, such a flow divider-combiner valve is often used in combination with a wheeled vehicle having at least two independently driven wheels. Each wheel of the vehicle is generally driven by a respective hydraulic motor. Each hydraulic motor is generally connected to the combiner side of such a valve as well as to the divider side. Independent connections between the flow-divider side of the valve and the respective hydraulic motors are made in a manner such that the flow divider-combiner valve supplies each hydraulic motor, independently, with hydraulic fluid. In addition, independent connections between the flow-combiner side of the valve and the respective motors are made in a manner such that the divider-combiner valve receives at least two independent streams or flows of hydraulic fluid from the separate hydraulic motors. Thus, the flow divider-combiner valve either independently supplies hydraulic fluid to or independently receives hydraulic fluid from each such hydraulic motor.
For such a wheeled vehicle, flow of hydraulic fluid through the valve causes each of the driven wheels to rotate at about the same speed and in the same direction. When flow of fluid is reversed through the valve, rotation of the wheels is similarly reversed. Thus, when equipped with a flow-combiner valve, the wheeled vehicle does not require a conventional transmission.
It is desirable that the divider-combiner valve cause the wheels to rotate at about the same speed so that the wheeled vehicle moves in a linear and predictable fashion.
Commercially available divider-combiner valves generally independently control flow of hydraulic fluid to each hydraulic motor by being responsive to pressures within and thereby accordingly adjusting or regulating the flows within the connections, lines or conduits supplying hydraulic fluid to or receiving hydraulic fluid from the hydraulic motors. A problem is encountered when using such commercially available divider-combiner valves, however, when one motor is subjected to a no-load condition (such as when its respective wheel is on ice) or when the vehicle is turning. Most of the commercially available divider-combiner valves react to such situations in two ways. First, as to the no-load condition, conventional divider-combiner valves generally respond to such a condition by reducing flow of hydraulic fluid through the no-load motor and by reducing flow through the other motor as well, resulting in the slowing down or stopping of the vehicle. Second, when the vehicle is directed around a corner, the wheel tranversing the greater arc causes its respective motor to act as a pump, in contrast to the motor guiding the vehicle through the turn. The motor which acts as a pump causes a low resistance to flow to be sensed at the conventional divider-combiner valve connected thereto. The divider-combiner valve responds by reducing the flow of hydraulic fluid to the motor guiding the vehicle through the turn. In addition, when the wheeled vehicle is directed around a corner, the wheel traversing the greater arc sometimes locks up, and upon being dragged across the ground by the wheel traversing the lesser arc, generally generates skid marks upon the ground, rug or such support surface.